Tunicates are a large group of marine animals and have been named “tunicate” because of cellosic outer covering called a tunic. They are divided into four major classes of the ascidians, thaliaceans, appendicularians and Sorberacea. Ascidians are the most diverse tunicate group. They are a rich source of secondary metabolites. Alkaloids are the major class of this compounds that mostly, display biological activity. Pyridoacridine alkaloids have a significant biological activities and their main mechanism is DNA cleavage inhibition by reactive oxygen species (ROS). The pyrroloacridine alkaloids are mostly cytotoxic and also, indole alkaloids have numerous biological properties such as potent antiviral, anti-inflammatory and cytotoxicity activities. Pyrrole Alkaloids exhibited several biological properties, like strong calmodulin antagonistic, antileukemic, inhibiting Na+/K+ ATPase, activating the octomyosin ATPase, and inducing release of Ca2+ from sarcoplasmic reticulum. Tunicates are a rich source of peptides, cyclic oligopeptides and depsipeptides such as patellamides, Didemnin, Iodocionin, Apliamides, Halocidin, Dicynthaurin or Clavanin, with significant biological activities. Some compounds extracted from tunicates such as, Glabruquionones, prenylhydroquinone, geranylhydroquinone, Longithorone, scabellones, and conithiaquinones have different structures of linear or cyclic hydroquinone and quinones. They possess a wide range of biological activities as strong anti- tumor, anti-leukemia, anti-oxidant, anti-viral, and selective cytotoxicity properties. Other numerous compounds with unique structures and different biological activities such as Phallusiasterols with modulating the PXR receptor Lepadins with antiplasmodial and antitrypanosomal properties Coproverdine with cytotoxic and anti-tumor activity and Ningalin with a strong inhibitory effects on CK1δ, CDK5 and GSK3β kinase, have been extracted from these animals. A large diversity of biological active compoundes from marine tunicates explains this realty that they have a large capacity to search and devalopement new marine medicinal compounds. It is hoped that in the future, marine drugs, have a greater portion in the drugstore shelves.